The present invention relates, in general, to electronics, and more particularly, to methods of forming semiconductor devices and structure.
Previously, the semiconductor industry utilized various methods and structures to form current sense circuits for power supply controllers. The current sense circuits generally received a load current that was regulated by the power supply controller and was applied to a load that was connected to power supply controller. The current sense circuits generally caused the load current to flow through a sense resistor and the sense resistor formed a voltage that was representative of the value of the load current. In some cases, it was desirable to use multiple sense resistors in order to select between different values of load currents. Typically, a transistor was connected in series with the sense resistor to steer the load current through the sense resistor and the transistor. One example of such a current sense circuit is disclosed in the data sheet for a step-up converter having a part number of MP1517 that was manufactured by Monolithic Power Systems, Inc., of Los Gatos, Calif. In most cases, the value of the sense voltage that was supplied to the power supply controller often varied and caused errors in the value of the load current.
Accordingly, it is desirable to have a current sense circuit that forms a current sense signal that more accurately represents the value of the load current.
For simplicity and clarity of illustration, elements in the figures are not necessarily to scale, and the same reference numbers in different figures denote the same elements. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. As used herein current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor or a cathode or anode of a diode, and a control electrode means an element of the device that controls current through the device such as a gate of an MOS transistor or a base of a bipolar transistor. Although the devices are explained herein as certain N-channel or P-Channel devices, a person of ordinary skill in the art will appreciate that complementary devices are also possible in accordance with the present invention. It will be appreciated by those skilled in the art that the words during, while, and when as used herein are not exact terms that mean an action takes place instantly upon an initiating action but that there may be some small but reasonable delay, such as a propagation delay, between the reaction that is initiated by the initial action.